Kendall Schmidt of Big Time Rush tried doing something really sweet for his fans ... but it didn't work out the way he planned.

TMZ reports that Schmidt is on tour with his side project, Heffron Drive, in Europe. When he flew to Austria from Orlando, Fla., he brought along about $7,000 worth of custom-made necklaces and bracelets for his fans -- but the bag holding jewelry went missing.

The luggage eventually showed up in Berlin, Germany, but the jewelry in the bag was still missing. Schmidt filed a claim with his airline in hopes of getting at least a cash reimbursement for the goodies that went MIA.

Schmidt talked about incident onstage in Vienna, Austria. "On my way here, they lost my suitcase," he shrugged. "I had a whole bunch of stuff in the suitcase that I was gonna throw out -- bracelets and stuff like that, all sorts of stuff -- even I lose bags on airplanes!"